A traditional differential assembly includes a first differential case half, a second differential case half, and a ring gear that are attached to each other to form a differential unit. A differential gear assembly is enclosed within a cavity formed within the first and second differential case halves. The first and second differential case halves are often referred to as a plain case half and a flange-side case half. A first tapered roller bearing is mounted to the flange-side case half and second tapered roller bearing is mounted to the plain case half.
The differential unit is installed into a carrier associated with a drive axle. Each of the first and second differential case halves includes a bearing journal that accepts a tapered roller bearing cone for the first and second tapered roller bearings. Bores in the carrier accept corresponding tapered roller bearing cups. The first and second tapered roller bearings are oriented such that an apex of each taper points in a direction away from the differential gear assembly.
One disadvantage with this traditional configuration concerns the first tapered roller bearing, which is associated with the flange-side case half. Packaging constraints prevent this flange-side bearing from favorably straddling gear forces, e.g. the flange-side bearing is positioned such that the flange-side bearing reacts most of the load from gear forces. This is especially true for a tandem axle configuration where a through-shaft, which transfers driving input to a rear-rear axle, passes through a hollow pinion input gear. To accommodate these high reaction forces, a large, high-cost bearing is required in order to meet durability requirements. The large reaction forces also result in high stress levels on a flange-side bearing journal. These stress levels in turn drive the need for more expensive differential case materials and/or expensive processing steps (induction hardening, for example) in order to meet durability requirements. This adds further cost to the product.
Another disadvantage with the traditional configuration is that assembly of the differential assembly into the carrier is highly constrained due to requirement of a one-piece flange-side bearing support. The one-piece flange-side bearing support is required because a two piece leg cap cannot package inside the available space. To assemble the differential assembly into the carrier, the differential assembly must be swung through an opening in a carrier housing such that the flange-side bearing and cone can be fitted into an associated cup. Sufficient clearances must be incorporated into the carrier housing to allow for the differential assembly to be installed without contacting any carrier structures. This increases the weight and cost of the carrier and increases the volume of the lubricant required.
Thus, there is a need for an improved differential configuration that facilitates assembly, reduces cost, and more evenly distributes gear loading, as well as overcoming other above-mentioned deficiencies in the prior art.